Excellent game! I've played the original Dr. Mario before, and I've played the SMS port here, so I decided to compare it to my experience with the original FC/NES version.
The visuals and music are probably my favorite part. The former is an excellent showcase of what the SMS is capable of, something many games from the era often didn't leverage hard enough. The latter is arguably on par with some Sega Pico tunes I've heard (namely the ones I've heard through VGM ripping them) and I mean this as a good thing; They're nice and chill and perfectly fit what's going on in the game. I wish there was a sound test or something (unless there is one, and I didn't see it) since I'd love to just listen to the tracks at my leisure outside of the gameplay.
Now my only criticism is really the play control/physics. Compared to Dr. Mario, the lack of DAS (Delayed Auto Shift), the inability to rotate the pills in the opposite direction, as well as being unable to rotate pills into certain gaps, or even just pause the game, makes it feel less responsive and more sluggish and janky to a more experienced player. I've considered using a debugger and a few other tools to implement a fix to the controls myself, but I've been busy with my own projects I need to finish, so I don't think I'd get to it anytime soon, plus I'd prefer to have the developer themselves give the approval or fix for such a thing.
Despite that, the game is, quite unironically one of the few games on the console I could justify playing for extended periods, it's that good compared to the rest of them! I would totally buy a physical copy if it released!
edit: I'm told the SMS version has better controls on a real SMS... And yet has issues on the Megadrive's compatibility mode, which is what I used to play this. That's really weird, since I haven't had this issue before.